Vertebrata

Vertebrata is a subphylum of the phylum Chordata, which includes species with a backbone or spinal column. This group includes the largest and most complex organisms on Earth, including humans and other mammals, birds, reptiles, amphibians, and fish.

Characteristics

Vertebrates are characterized by their vertebral column, or backbone, which is made up of individual vertebrae. This structure provides support and protection for the spinal cord, which is a key part of the nervous system. Other defining characteristics of vertebrates include a well-developed head, a closed circulatory system, and an endoskeleton that allows for growth and movement.

Classification

Vertebrates are divided into two groups: Agnatha, which includes jawless fish like lampreys and hagfish, and Gnathostomata, which includes all vertebrates with jaws. Gnathostomata is further divided into several classes, including Mammalia (mammals), Aves (birds), Reptilia (reptiles), Amphibia (amphibians), and Pisces (fish).

Mammalia

Mammals are characterized by their ability to produce milk, hair or fur, and a unique jaw structure. This class includes a wide range of species, from mice and elephants to humans.

Aves

Birds are characterized by their feathers, beaks, and hard-shelled eggs. They are the only group of vertebrates capable of sustained flight.

Reptilia

Reptiles are characterized by their scales, cold-blooded metabolism, and hard-shelled eggs. This class includes turtles, lizards, snakes, and crocodiles.

Amphibia

Amphibians are characterized by their ability to live both in water and on land, and their life cycle typically involves a larval stage in water. This class includes frogs, toads, salamanders, and newts.

Pisces

Fish are characterized by their gills, fins, and scales. They are the most diverse group of vertebrates, with thousands of species living in a wide range of aquatic environments.

Evolution

The first vertebrates appeared in the Cambrian period, over 500 million years ago. They have since evolved into a wide range of forms, adapting to life in nearly every environment on Earth.

See also

• Chordata
• Invertebrate
• Animal